1. Field of the Invention
This invention relates to a fluid heating apparatus which provides increased overall thermal efficiency by using a baffle arrangement to direct flue gas flow about a rear wall, side walls and a bottom wall of a fluid container.
2. Description of Prior Art
Conventional heating apparatuses and processes for deep fat fryers operate at an overall thermal efficiency of about 40 percent. The exhaust or flue gases of such conventional apparatuses and processes operate at approximately 1300.degree. F., and include nitrogen oxide emissions of approximately 70 ppm. Many conventional deep fat fryers operate with an open flame positioned directly beneath the fluid container. Such apparatuses are extremely dangerous and relatively inefficient.
U.S. Pat. No. 4,898,151 discloses a fuel-fired deep fat frypot in which exhaust gases are recirculated around the frypot. A squirrel cage type centrifugal fan is used to draw ambient air and gas through a burner and into a combustion chamber. Relatively hot combustion gases are discharged into an inlet chamber. The combustion gases flow rearwardly through side heating passages which are defined by an insulation structure. The combustion gases continue to flow into a rear plenum. The hot combustion gases are then drawn into a return plenum side of an impeller inlet where the hot combustion gases are mixed with combustion gas emanating from the burner, and such mixture is introduced back into the fan impeller inlet.
U.S. Pat. No. 4,751,915 discloses a gas-fired fryer and gas-fired burner for the fryer. Combustion products are routed from an outlet portion of a conduit, along outer surfaces of an end wall of the frypot, then along outer surfaces of side walls of the frypot. The channels terminate in respective outlets for the combustion products.
U.S. Pat. No. 4,848,318 teaches a cooking apparatus with a frypot for heating cooking oil. An array of flow directing vanes and heat transfer fins are used to increase heat transfer from the combustion gases to the cooking oil.
U.S. Pat. No. 4,913,041 relates to a deep fat frying apparatus having solid insulation material which forms combustion gas heating passages along exterior surfaces of well sections of the frypot. Hot combustion gases are discharged from the burner assembly into a heating cavity, and then into an inlet portion of the heating passage system. The combustion gases continue to flow through the passage system in multiple passes along lateral outwardly facing wall surfaces of the well section, and then flow outwardly through a metal retaining jacket structure into a suitable exhaust header.
U.S. Pat. No. 4,690,127 teaches a catalytic combustion deep fat fryer wherein a heat transfer device is defined by a hollow, elongated heat exchanger having a generally oval, vertical cross-sectional interior configuration, a combustion end portion, and a flue end portion. U-shaped fins are connected with an inner side wall surface of the heat exchanger.
Conventional deep fat fryers and other heating apparatuses, as discussed above, do not teach or suggest a baffle arrangement which is used to direct flue gases in one flow direction, then in a counterflow direction. Such conventional heating apparatuses also do not teach or suggest use of either a power burner or a pulse combustor for generating heat and reducing undesirable emissions, such as nitrogen oxides and carbon monoxide.